For energy conversion systems, the conversion efficiency of the power supplies is of great importance. Compared with conventional power conversion circuits, the bridgeless circuits can eliminate part or all of diodes, thus reducing the conduction losses of the circuits, and exhibiting advantages in efficient energy conversion. As a kind of bridgeless circuit, the Totem-Pole bridgeless circuits have such advantages as simple circuit structure and high conversion efficiency, and thus have been increasingly applied in recent years.
FIGS. 1a and 1b illustrate circuit diagrams of a Totem-Pole bridgeless circuit. Take FIG. 1 as an example, the first bridge arm unit 210 and the second bridge arm unit 220 are connected to each other in parallel. The first bridge arm unit 210 includes two switch tubes S1, S2 which are connected in series in the same direction. The second bridge arm unit 220 includes two diodes D1, D2 which are connected in series in the same direction. A power supply AC1 and an inductor L1 are positioned between a connection point of the two switch tubes and a connection point of the two diodes. A capacitor C1 and a load RL are first connected in parallel and then are in parallel connection to the first bridge arm unit 210 and the second bridge arm unit 220.
In the Totem-Pole bridgeless circuits, a main challenge is to sample the inductive current whereby achieving the control of the timing sequence of the switch tubes S1, S2.